In electrophotography, a toner to which an electric charge has been given by rubbing with carrier particles is moved onto an electrostatic latent image with the opposite electric charge on a photosensitive member, and the imaged toner is then transferred onto a substrate like paper to realize the image. The substrate is then contacted with a heat roll to fix the image on the substrate. The heat roll is made from a material to which the toner does not adhere, but there is still a problem that a portion of the toner is adhered on the heat roll and will leave a thin image on the next substrate, which is called "off set".
In order to avoid the off set, Japanese Kokai Publication 106073/1989 proposes that silicone-containing polymer microparticles be mixed with a toner mixture. However, it takes a long period of time to form a uniform mixture of the silicone-containing polymer microparticles and the toner mixture. The resulting toner mixture may often cause blocking of toner particles. If carrier particles are also mixed in the toner mixture, the silicone-containing polymer microparticles are adhered onto the carrier particles and adversely affect the charge properties of the carrier particles.
Japanese Kokai Publication 137264/1989 discloses that a toner is prepared by a suspension-polymerization in the presence of a remover polymer, such as silicone oil, mineral oil and the like. In this technique, however, the remover polymer is unstable in a polymerization system and therefore adversely affects the blocking properties of the toner. The amount of the remover polymer introduced has a certain limitation, or is insufficient.